A paramilitary leader in Northern Ireland is murdered. Can the moderates prevail?

Edward Treanor, a 31-year-old civil servant, was enjoying a New Year's Eve drink with his new girlfriend at her pub, the Clifton Tavern in Catholic North Belfast. At 9:07 p.m. two masked men, one armed with a submachine gun, the other with a pistol, burst in and began firing indiscriminately at the customers. Treanor was hit in the head and died before he could greet the new year--a new year that starts off with an ill omen for peace in Northern Ireland.

Catholics in the province had been bracing for attacks ever since the Dec. 27 murder of Billy Wright, leader...